* ext4 offers less blocks than other fs
@ 2011-11-15 19:51 Jan Engelhardt
2011-11-16 1:43 ` Yongqiang Yang
2011-11-16 3:20 ` Eric Sandeen
0 siblings, 2 replies; 3+ messages in thread
From: Jan Engelhardt @ 2011-11-15 19:51 UTC (permalink / raw)
To: linux-ext4
Hi.
In moving away from some ntfs-3g filesystem to ext4 (migration of a
Windows-esque fileserver), I see a rather steep metadata use with ext4
such that moving the data was not completely possible. Per df:
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/dm-5 1953514324 1952543856 970468 100% /mnt/old
/dev/mapper/data 1922858888 1922858880 0 100% /mnt/new
[attempted a rsync as root]
The blockdev size is just minimally different:
20:32 nas:~ # blockdev --getsize64 /dev/dm-5
2000398671872
20:32 nas:~ # blockdev --getsize64 /dev/dm-6
2000396836864
And there is a 29 GB(!) difference between 1953514324 and 1922858888,
so my question is: where is all of that going?
(e2fsprogs 1.41.14)
Filesystem volume name: data
Last mounted on: /mnt/new
Filesystem UUID: 807fec49-7a8a-3520-a648-be677475377c
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype
needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg
dir_nlink extra_isize
Filesystem flags: signed_directory_hash
Default mount options: (none)
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 122101760
Block count: 488378134
Reserved block count: 24418906
Free blocks: 480664715
Free inodes: 122101749
First block: 0
Block size: 4096
Fragment size: 4096
Reserved GDT blocks: 907
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 8192
Inode blocks per group: 512
Flex block group size: 16
Filesystem created: Mon Nov 14 20:43:23 2011
Last mount time: Mon Nov 14 20:43:55 2011
Last write time: Mon Nov 14 20:43:55 2011
Mount count: 1
Maximum mount count: 26
Last checked: Mon Nov 14 20:43:23 2011
Check interval: 15552000 (6 months)
Next check after: Sat May 12 21:43:23 2012
Lifetime writes: 144 MB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: 5e2619e2-7683-4589-b390-57e569444705
Journal backup: inode blocks
Journal features: (none)
Journal size: 128M
Journal length: 32768
Journal sequence: 0x00002751
Journal start: 4341
[Details about groups 0-14904 omitted.]
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: ext4 offers less blocks than other fs
2011-11-15 19:51 ext4 offers less blocks than other fs Jan Engelhardt
@ 2011-11-16 1:43 ` Yongqiang Yang
2011-11-16 3:20 ` Eric Sandeen
1 sibling, 0 replies; 3+ messages in thread
From: Yongqiang Yang @ 2011-11-16 1:43 UTC (permalink / raw)
To: Jan Engelhardt; +Cc: linux-ext4
On Wed, Nov 16, 2011 at 3:51 AM, Jan Engelhardt <jengelh@medozas.de> wrote:
> Hi.
>
>
> In moving away from some ntfs-3g filesystem to ext4 (migration of a
> Windows-esque fileserver), I see a rather steep metadata use with ext4
> such that moving the data was not completely possible. Per df:
>
> Filesystem 1K-blocks Used Available Use% Mounted on
> /dev/dm-5 1953514324 1952543856 970468 100% /mnt/old
> /dev/mapper/data 1922858888 1922858880 0 100% /mnt/new
> [attempted a rsync as root]
>
> The blockdev size is just minimally different:
> 20:32 nas:~ # blockdev --getsize64 /dev/dm-5
> 2000398671872
> 20:32 nas:~ # blockdev --getsize64 /dev/dm-6
> 2000396836864
>
> And there is a 29 GB(!) difference between 1953514324 and 1922858888,
> so my question is: where is all of that going?
>
> (e2fsprogs 1.41.14)
> Filesystem volume name: data
> Last mounted on: /mnt/new
> Filesystem UUID: 807fec49-7a8a-3520-a648-be677475377c
> Filesystem magic number: 0xEF53
> Filesystem revision #: 1 (dynamic)
> Filesystem features: has_journal ext_attr resize_inode dir_index filetype
> needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg
> dir_nlink extra_isize
> Filesystem flags: signed_directory_hash
> Default mount options: (none)
> Filesystem state: clean
> Errors behavior: Continue
> Filesystem OS type: Linux
> Inode count: 122101760
> Block count: 488378134
> Reserved block count: 24418906
> Free blocks: 480664715
> Free inodes: 122101749
> First block: 0
> Block size: 4096
> Fragment size: 4096
> Reserved GDT blocks: 907
> Blocks per group: 32768
> Fragments per group: 32768
> Inodes per group: 8192
> Inode blocks per group: 512
> Flex block group size: 16
> Filesystem created: Mon Nov 14 20:43:23 2011
> Last mount time: Mon Nov 14 20:43:55 2011
> Last write time: Mon Nov 14 20:43:55 2011
> Mount count: 1
> Maximum mount count: 26
> Last checked: Mon Nov 14 20:43:23 2011
> Check interval: 15552000 (6 months)
> Next check after: Sat May 12 21:43:23 2012
> Lifetime writes: 144 MB
> Reserved blocks uid: 0 (user root)
> Reserved blocks gid: 0 (group root)
> First inode: 11
> Inode size: 256
> Required extra isize: 28
> Desired extra isize: 28
> Journal inode: 8
> Default directory hash: half_md4
> Directory Hash Seed: 5e2619e2-7683-4589-b390-57e569444705
> Journal backup: inode blocks
> Journal features: (none)
> Journal size: 128M
> Journal length: 32768
> Journal sequence: 0x00002751
> Journal start: 4341
> [Details about groups 0-14904 omitted.]
Hi,
The system metadata can be calculated.
The inode blocks per group is 512, besides there are 1 block bitmap
block and 1 inode bitmap block per group. The above filesystem has
488378134 blocks, thus there are 14905 block groups. So the group
tables (inode table, inode bitmap, block bitmap) take up 7661170
blocks. In addition, journal uses 32768 blocks and group descriptor
uses some blocks.
Yongqiang.
> --
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>
--
Best Wishes
Yongqiang Yang
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: ext4 offers less blocks than other fs
2011-11-15 19:51 ext4 offers less blocks than other fs Jan Engelhardt
2011-11-16 1:43 ` Yongqiang Yang
@ 2011-11-16 3:20 ` Eric Sandeen
1 sibling, 0 replies; 3+ messages in thread
From: Eric Sandeen @ 2011-11-16 3:20 UTC (permalink / raw)
To: Jan Engelhardt; +Cc: linux-ext4
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On 11/15/11 1:51 PM, Jan Engelhardt wrote:
> Hi.
>
>
> In moving away from some ntfs-3g filesystem to ext4 (migration of a
> Windows-esque fileserver), I see a rather steep metadata use with ext4
> such that moving the data was not completely possible. Per df:
>
> Filesystem 1K-blocks Used Available Use% Mounted on
> /dev/dm-5 1953514324 1952543856 970468 100% /mnt/old
> /dev/mapper/data 1922858888 1922858880 0 100% /mnt/new
> [attempted a rsync as root]
>
> The blockdev size is just minimally different:
> 20:32 nas:~ # blockdev --getsize64 /dev/dm-5
> 2000398671872
> 20:32 nas:~ # blockdev --getsize64 /dev/dm-6
> 2000396836864
extN filesystems preallocate a lot of metadata, vs other filesystems
which may allocate this on the fly; that is what you are seeing.
> And there is a 29 GB(!) difference between 1953514324 and 1922858888,
> so my question is: where is all of that going?
Yongqiang Yang has it right; 7661170 + 32768 blocks for metadata
is right at 29G.
- -Eric
> (e2fsprogs 1.41.14)
> Filesystem volume name: data
> Last mounted on: /mnt/new
> Filesystem UUID: 807fec49-7a8a-3520-a648-be677475377c
> Filesystem magic number: 0xEF53
> Filesystem revision #: 1 (dynamic)
> Filesystem features: has_journal ext_attr resize_inode dir_index filetype
> needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg
> dir_nlink extra_isize
> Filesystem flags: signed_directory_hash
> Default mount options: (none)
> Filesystem state: clean
> Errors behavior: Continue
> Filesystem OS type: Linux
> Inode count: 122101760
> Block count: 488378134
> Reserved block count: 24418906
> Free blocks: 480664715
> Free inodes: 122101749
> First block: 0
> Block size: 4096
> Fragment size: 4096
> Reserved GDT blocks: 907
> Blocks per group: 32768
> Fragments per group: 32768
> Inodes per group: 8192
> Inode blocks per group: 512
> Flex block group size: 16
> Filesystem created: Mon Nov 14 20:43:23 2011
> Last mount time: Mon Nov 14 20:43:55 2011
> Last write time: Mon Nov 14 20:43:55 2011
> Mount count: 1
> Maximum mount count: 26
> Last checked: Mon Nov 14 20:43:23 2011
> Check interval: 15552000 (6 months)
> Next check after: Sat May 12 21:43:23 2012
> Lifetime writes: 144 MB
> Reserved blocks uid: 0 (user root)
> Reserved blocks gid: 0 (group root)
> First inode: 11
> Inode size: 256
> Required extra isize: 28
> Desired extra isize: 28
> Journal inode: 8
> Default directory hash: half_md4
> Directory Hash Seed: 5e2619e2-7683-4589-b390-57e569444705
> Journal backup: inode blocks
> Journal features: (none)
> Journal size: 128M
> Journal length: 32768
> Journal sequence: 0x00002751
> Journal start: 4341
> [Details about groups 0-14904 omitted.]
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
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2011-11-15 19:51 ext4 offers less blocks than other fs Jan Engelhardt
2011-11-16 1:43 ` Yongqiang Yang
2011-11-16 3:20 ` Eric Sandeen
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